Control system



p i 30, 19 6. J. P. HOUCK Em 2,399,351

CONTROL SYSTEM Filed April 21, 1945 3 Sheets-Sheet 1 WITNESSES:INVENTORS April 30, 1946.

J. P, HoucK ETAL CONTROL SYSTEM 3 Sheets-Sheet 2' Filed April 21, 1945WITNESSES: 54% J E Z 5 m WWW M T6. ZN mL/ V .0 m ma m .2 WW JP April 30,1946. J H U K ET AL 2,399,351

CONTROL SYSTEM Filed April 21, 1945 3 Sheets-Sheet 3 5'0 fec fire Der/c6 Loz L l L96 390 INVENTO R5 ,famaPf/oucx and Fer/,6? 566/36/0700,

Patented Apr. 30, 1946 James P. Bond: and Ralph A. Geiselman, Pltts-'burgh,'Pa., assignors to Westinghouse Electric Corporation, EastPittsburgh, Pa., a corporation of Pennsylvania Application April 21,1945, Serial No. 589,664

13 Claims.

This invention relates to control systems and in particular to controlsystems utilized in conjunction with are furnace regulators.

Heretofore, it has been common practice to supply are furnaces through apower transformer disposed to be connected through a cir cult breaker toa source of powersupply. The

operators of the arc furnaces are not always skilled in the operation ofthe switching equipment and numerous breaker failures have beenencountered because of the improper operation of the breaker. Forexample, when a short. circuit isencountered as by reason of one or moreof the electrodes being in contact withthe furnace charge, the operatoroften tries to reclose the circuit breaker before the short circuitedelectrode is raised to a position to clear the charge. If the breaker isrepeatedly closed against the fault, fiashover within the breakerhousing is encountered and the breaker is damaged.

An object of this invention is to provide in a control system for arcfurnaces for regulating the feeding of an electrode and to control theoperation of a circuit breaker to prevent its re closing for theduration of a fault.

Another object of this invention is to provide for controlling theoperation of a circuit breaker in the supply circuit to an arc furnaceto prevent the reclosing of the circuit breaker unless the furnace isfree of short circuit faults.

A more specific object of this invention is to provide a system andapparatus for preventing the operation of a circuit breaker inthe-supply circuit to an arc furnace to prevent the reclosing of thecircuit breaker unless the furnace is free of short circuit faults andto insure the raising of the electrode in the furnace to clear thefault.

Other objects of this invention will become apparent from the followingdescription when taken in conjunction with the accompanying drawings, inwhich:

Figures 1A and 13 form a composite drawing illustrating diagrammaticallythe circuits and apparatus utilized in an embodiment of this invention;

Fig. 2 is a diagrammatic illustration of limit switches employed inconjunction with the circuits of Figs. 1A and 1B, and

Fig. 3 is a diagrammatic illustration of the circuits and apparatusembodying the teachings of this invention as applied to an arc furnacehaving a diiferent regulating system than the embodiment of Figs. 1A and13.

Referring to Figs. 1A and 1B of the drawings,

' negative symbols.

an electric furnace I0 is illustrated, the furnace comprising areceptacle l2 containing a charge I4 and three movable electrodes l6, l8and 29. The electrodes l6, I8 and 20 are connected by conductors 22, 24and 26, respectively, to the sec ondary windings ofa power transformer28, the primary windings of which are disposed to be connected throughthe'contact members 30, 32 and 34 of a circuit breaker 36 to a source ofpower supply (not shown). As illustrated flexible cables 38, 40 andconnected to electrodes [6, l8 and 20, respectively, are disposed to bewound on winding drums 44, 46 and 48, respectively, which are disposedto be operated by motors 50, 52 and 54, respectively.

The motors 5|], 52 and 54 comprise armature members 56, 58 and 60,respectively, and field windings 62, 64 and 66, respectively, the fieldwinding of each motor being connected to an energizing sourcerepresented by the positive and In order to supply energy to thearmature windings 56, 58 and 60, the armature windings are connectedacross the armature windings 68, 10 and 12, respectively, of maingenerators l4, l6 and 18, respectively. The main generators l4, l6 and18 are provided withfield windings 80, 82 and 84, respectively, whichare connected to be supplied with energy from armature windings 86, 88and 90, respectively, of exciter generators 92, 94 and 96, respectively.Each of the main generators and its associated exciter generator isdisposed to be driven by a motor in accordance with well known practice,the motors not being shown for simplicityof the drawings.

In the embodiment illustrated, each of the exciter generators 92, 94 and96 is illustrated as having four field windings although other forms ofthe exciter generators or combination of main generator and excitergenerator may be utilized as long as the exciter is provided with twoopposed control field windings as will be described. The excitergenerator 92 is provided with two opposed control field windings 98 andHill, a self- ,excited field winding I02 connected in shunt relation tothe armature winding 86 and a differential field winding I04 connectedto be energized in accordance with the output voltage of the maingenerator 14.

Likewise, the exciter generator 94 is provided with two opposed controlfield windings 'IOBand I08, a self-excited field winding H0 and adifferential field winding H2 and the exciter generator 96 is providedwith two opposed control field windings H4 and H5, a self-excitedwinding H8 and a differential field winding I20.

The control field windings 93, I26 and H4 are shown connected acrossrectifiers I22, I24 and I26, respectively, to b supplied therefrom witha unidirectional cur .znt that is a measure of the alternating currentflowing through phase conductors 22, 24 and 2 5, respectively, in amanner hereinafter described, Whereas the control field windings I39,I98 and IIS are connected across rectifiers I23, I30 and I32,respectively, which are disposed to be connected to supply energy thatis a measure of the drop in voltage across the arc of electrodes I5, I 8and 20, respectively.

In the system of Figs. 1A and 1B the connections to the rectifiers I22,I24 and I231: and to rectifiers I23, I36 and I32 are ccntrolledin apredetermined manner by the operation of one or more switching apparatussuch as the electromagnetic switching device I34, the master controllerI36, the independent phase manual controllers. I38, I43 and I42 and thecircuit break er 36.

As illustrated, the master controller I33 may be employed for socontrolling the excitation of exciter generators S2, 94 and 93 as toeffect-a simultaneous change in the operation or the electrode motor asto simultaneously raise or lower the electrodes 56, I8 and 29,respectively, depending upon the direction in which thecontroller I36 ismanually actuated. The master controller I36 is provided with segmentsMIL-I46, HIE-459 and I52-I54 disposed in the off position for connectingthe control field windings of exciter generators 92, 94 and 96respectively, to sources of energy, and segments I56--I5B- -I69, I62-I64I66, and I38--IIIl-II2 disposed in the raise position associated withgenerators 92, 94 and 96-, respectively, and segments II4--IIG I18,I8D-I82I84 and IS6I88I9Il-, respectively, disposed in the lowerposition. In addition to these segments, a segment I92 is also providedin the off position, the purpose of which will become apparenthereinafter.

The controllers I38, I40 and I42 are similar in construction. Thecontroller. I42 comprises a drum I94 disposed for predeterminedrotational and slidable movement whereby segments I96- I98 or segments239-292-2Il4 areselectively moved to raise or lower or to 0ff" orautomatic positions. In the'position shown, the controller I42 is in theautomatic positionwith the segments of the drum out of alignment withthepairs of. contact fingers. which they will bridge in the raise or lowerpositions. In the automatic position, three contact members 296, 238 and2H engage contact fingers whereby control of the energization of thecontrol field windings H4 and H6 lies in the operation of theelectromagnetic switching device I34, the circuit breaker 36'and themaster controller I36.

With the handle 2I2 of the controller I42 in the automatic position, afinger 2I4 carried by the shaft 2I6 is positively held by opposedsprings on one side of an arcuate stop plate 2I8 to maintain a springmember 220 compressed between the drum I94 and a stop 222. The arcuatestop plate ZIB is provided with a notch 224 50 positioned that When thehandle 2I2 is manually moved to the off position, the finger 2I4 ismovedto a position where it is in alignment with the notch 224 andpasses therethrough to the other side of the arcuate stop member 2 I8and the force of the spring 220 eiTects a sliding movement of the drum94 and segments thereon to a position where the segments can bridgeassociated pairs of contact fingers when the handle 2I2 is rotated tothe "raise or lower positions. The segments 225, 228, 233, 232 and 234of controller I40 and segments 236, 238, 243, 242 and 244 of controllerI38 correspond to segments I96, I98, 293, 232 and 234, respectively, ofcontroller I42, controller I46 also being provided with contact members243, 243 and 253 and controller I38 with contact members 252, 254andI256 corresponding to contact members 2B6, 20B and 2H3, respectively,of controller I42.

In order to control the operation of the circuit breaker 36, a relaysystem comprising the relays 253, 263 and 232 and the electromagneticswitching device I34 is utilized. The relay 253 issprovided with awindin234 grounded at one end as at340' and connected across the secondarywindin ofatransformer 236 the primary winding of which is disposed to beconnected through a switch 238 to a source of supply. When energized thecontact member 279 oi. the relay 258 is disposed to connect theenergizing winding 212 of the switching device I34 across a source ofsupply represented by the positive and. negative symbols. Theelectromagnetic switching device I34 is provided with a contact member2'54 disposed when a manually operated switch 213 is in a circuitclosing position and the winding 272 is energized to establish a circuitextending from the positive terminal of a source of supply. (not shown)through the switch 213, contact member 214 of the device I34, contactmember 278 of relay 233 and the energizing winding 28?! of relay 262 tothe negative terminal of the source of electrical energy to actuate thecontact member 282 of relay 232 to a circuit closing position. Thecontact member 282 thus establishes a circuit through the winding 284 ofa circuit breaker to effect the operation of the circuit breaker tocause the ings of the different exciter generators.

contactim'embers 3'9, 32 and 34 of the breaker 36 to connect the powertransformer 28 to the source of power supply.

The electromagnetic switching device 534 is provided with a number ofcorresponding contact members for controlling the circuits to therectifiers supplying the opposed control field wind- Thus contact'membersZSB, 233 and 23D aredisposed to be in open circuit position whenthe winding 2'12 is deenergized to interrupt the circuit to rectifiersI28, I30 and I32, respectively. Contact members 292-294, 295-233, and333-392 associated with rectifiers I22, I 24 and 25, respectively, arealso disposed to be in the open circuit position when theelectromagnetic switching device I3'4 is deenergized whereas contactmembers 304-433, 3il83|0 and 3I23I4, respectively, are in circuitclosing position with respect to their associated rectifiers I22, I24and I26, respectively.

Again referring to the circuit breaker 33, the breaker is provided withcontact members 313, 3 I8, 320, 322 and 324 disposed in a circuitopening position and a contact member 325 disposed in a circuit closingposition when the main contact members 39, 32 and 34 of the breaker 39are in a circuit opening position.

The contact member 3I6 functions when the circuit breaker 36 is in acircuit closing position to connect one end of the energizin winding 329of an electro-magnetic trip device 339 to a terminal of a source ofelectrical energy, the other end of winding 328 being disposed to beconnected through a trip switch 332 to the other terminal of the sourceof electrical energy.

As illustrated, the circuit breaker 36 carries a lug 334 disposed tomove upwardly as the circuit breaker closes to slide beyond a latch 336carried by the trip device 338 whereby the latch 336 engages the lug 334to hold the breaker in a circuit closing position untilithe winding 328is energized to release the latch and consequently the circuit breaker.

The contact member 3 I8 carried by the breaker 36 is disposed to closean energizing circuit throughthe energizing winding of relay 268 whenthe switch 216 is in a circuit closing position and the circuit breaker36 is actuated to its circuit closing position wherebycontact member 218is disposed in a circuit closing position when the breaker 36 is in anopen circuit position to establish a circuit extending from one end ofthe winding 264 of relay 258 to conductor 24 whereby the winding 264 iseffectively deenergized when a short circuit of any one of theelectrodes I6, I8 and 28 in the furnace is encountered. This is apparentfor if one end of winding 264 is'grounded as at 338, the other end willbe grounded through contact member 326, conductor 24, through thesecondarywindings of the transformer 28, con- 1 ductor 22 or 26,electrode [6 or I8 and the grounded furnace or directly throughconductor 24 and electrode l8 to the grounded furnace depending uponwhich of the electrodes is short circuited. 01' course, if a shortcircuit condition does i not exist in the furnace, the winding 264 willnot be deenergized when the contact member 326 is in a circuit closingposition unless the switch 268 is moved to a circuit opening position todeenergize the transformer 266.

In addition to the trip switch 332, the electromagnetic trip device 338is disposed to be energized and operated by an overload condition in thefurnace I8. For this purpose, an overload protective device 348 isprovided, being connected through current transformers 342, 344 and 346associated with conductors 22, 24 and 26, respectively, and having acontact member 348 disposed upon the occurrence of a predeterminedoverload condition such as the flow of a predetermined current in anyone of the conductors 22, 24 and 26, to be actuated to a circuit closingposition to establish an energizing circuit for the winding 328 to tripthe circuit breaker 36.

With the circuit breaker 36, the electromagnetic switching device I34,the master controller I36 and the individual controllers I38, I48 andI42 as described, therectifiers I22, I24 and I26 are disposed to beconnected to be supplied from the current transformers 358, 352 and 354,respectively, associated with conductors 2 2, 24 and 26, respeci tively,whereas the rectifiers I28, I38 and I32 are source of electrical energyto cause the operation of the electrode motors to raise the electrodes.

' In order to provide for limiting the amount of movement of theelectrodes in the raise and lower directions, suitable limit switchesmay be disposed to be operated by the movement of the electrodes tointerrupt the circuits to the rectifiers associated with the opposedcontrol fields of the respective exciter generators or to interrupt thefield circuit itself. As an example of the use of limit switches,reference may be had to Fig. 2 of the drawings whereinlimit-switches 356and 358 are disposed to be operated by a projection 368 carried byelectrode 28 to interrupt the circuits to fieldwindings H4 and H6,respectively, depending upon the direction of movement of the electrode28. Similar limit switches (not shown) are provided for electrodes I6and I8, it being understood that such limit switches are employed inconjunction withthe circuitof Figs. 1A and 1B but are not shown thereonin order to simplify the drawings. V

In operation, with the circuits and apparatus asshown, the switch 268 ismoved to a circuit closing position to supply power to transformer 266,whereby the winding 264 of the relay 258 is energized to actuate thecontact member 218to a circuit closing position. The contact member 218establishes an energizing circuit for the winding .232 'ofelectromagnetic switching device I34 whereby contact members 214, 286,282, 284, 288, 296, 298, 298, 388 and 382 of the switching device I34are actuated to circuit closing positions and the contact members 384,386, 388, 3I8, 3I2 and 3I4 of the switching device I34 are actuated tocircuit opening positions.

The movement of the contact member 214 of the switching device I34 setsup an energizing circuit for the winding 288 of relay 262 which may beestablished by the manual operation of the switch 216 to a circuitclosing position. With the winding 280 of relay 262 thus energized, thecontact member 282 of relay 262 is actuated to a circuit closingposition to establish the energizing circuit for the winding 284 ofcircuit breaker 36, whereby the contact members 38, 32, 34, 3I6, M8,328, 322 and 324 of the circuit breaker are actuated to circuit closingpositions and the contact member 326 is actuated to a circuit openingposition.

As the circuit breaker 36 moves to the circuit closing position for thecontact members 38, 32 and 34', the lug 334 carried by the circuitbreaker slides over the latch 336 of the trip device 338 and is engagedthereby to hold the circuit breaker 36 in circuit closing position untilthe winding 328 of th trip device 338 is energized to effect thetripping of the breaker.

The electrodes I6, I8 and 28 are lowered toward the charge l4 in thefurnace I8 by moving the master controller I36 to the lower positionwhere segments I14, I16, I18, I88, I82, I84, I86,

.I88 and I98 are in engaging relation with cooperating contact fingerswhereby circuits are established from separate sources of electricalenerg represented by the positive and negative symbols associated witheach set of segments through rectifiers I28, I38 and I32 to effect theenergization of the control field windings I 88, I88 and I I6,respectively. With control field windings I88, I88 and H6 energized inthis manner the exciter generators 92, 94 and 86, respectively, are soexcited as to control the excitation of the main generators 14, 16 and18, respectively, to effect the operation ofthe electrode motors 58, 52and 54,

respectively, tothe lower ofthe electrodes I6, I8 and-28 respectively.These circuits may be. traced from the positive symbol shown below eachof the controllers I38, I48 andv I42 through segments I18, I84 and-I98-of the master controller I36 to a terminal of the rectifiers I28,I38 and I 32,.respectively, from the opposite terminal of the rectifiersthrough contact members 286, 288 and 298, respectively, or theelectromagnetic switching device I34, segments I15, I82and I88,respectively, of the master controller I36 to the negative terminals ofthe. separate sources of supply.

The motors 58, 52 and 54 are thus operated to lower the electrodes. I8,I8 and 28, respectively, until an arc is established, at which time themaster controller I36 is returned to its oil posi tion and the. opposedcontrol field windings of the exciter generators 92, 94 and. 96,respectively, assume the automatic regulation of the positioning of theelectrodes I6, I8 and 28.

Under the conditions of automatic operation, the field windings I88, I88and II 6 are supplied by the rectifiers I28, I38 and I32, respectively,these rectificrs being connected by circuits which extend fromconductors 22, 24 and 26, respectively, through contact members 324, 322and 328, respectively, of the breaker 35, contact members 252, 246 and286, respectively, of the controllers I38, I48 and I42, respectively,segments I44, I 48 and I52, respectively, of the master controller I35,contact members 286, 288 and 298, respectively, of the electromagneticdevice I34 through the rectifiers I28, I38 and I32, respectively,contact members 254, 248'and 288, respectively, of the individualcontrollers to the common segment I92 of master controller I and fromthence t ground.

At the same time, the control field windings 88, I88 and H4 of theexciter generators 92, 84 and 86. respectively, are supplied fromrectifiers I22, I24 and I26, respectively, which are connected incircuits extending from the current transformers 358, 352 and 354through contact members 256, 258 and 2I8, respectively, of thecontrollers I38, I48 and I42, respectively, segments I46, I58 and I54,respectively, of the master controller I38, contactmembers 284, 298 and382, respectively, of the electromagnetic switching device I34, throughthe rectifiers I22,.I24 and I26, respectively, contact members 292, 286and 388, respectively, of the switching device I34, contact members 254,248 and 288, respectively, of the controllers I 38, I48 and'l42,respectively, to the common segment I82 of the master controller I35 andfrom thence to ground, whereby the field windings 98, I88 and II4 areenergized in accordance with a measure of the current flowing in theconductors 22, 24 and 28, respectively.

With the electrodes I5, I8 and 28 properly positioned in the furnace I8,the are potential and arc currents are properly balanced so that theopposed. control field windings 98--I88, I86-I88 and I I4I l8 ar inbalance and the motors 58, 52 and 54, respectively, are not operated. Antendency toward unbalanced relation between the arc current and arepotential immediately causes a change in the excitation of the excitergenerators to effect immediate operation of the electrode motors toposition the electrodes associated therewith so as to maintain an arehaving a predetermined are potential and are current.

If, during the operation of the arc furnace, one or more of theelectrodes should become short circuitedas by reason of a cave-in of thecharge I4 against oneormore of the electrodes, the increase in currentflowing through the conductor 22, 24 or 26 supplying the electrode thusshort circuited effects operation of the protective device 348150actuate the contact member 348 to a circuit closing position to effectthe energization of the winding 328 of the trip device 338 torelease thecircuit breaker 38 and'interrupt the supply of power to the powertransformer 38. The movement of the circuit breaker 36 to the opencircuit position for interrupting the power supply causes the contactmember 328 to move to a circuit closing position to close a circuit fromthe ungrounded end of winding 264 of the relay 258 through the contactmember 326 to conductor 24 and from thence to ground through the shortcircuited electrode and the grounded receptacle I2.

The closing of the ground circuit by the contact member 326 effectivelyshunts the winding 264 of relay 258 whereby the winding is deenergizedand the contact member 2'78 moves to a circuit opening position toeffect the deenergization of the winding 272 of the electromagneticswitching device I34. With the switchingdevioe I34 ius deenergized,contact members 214', 285, 292, 28 i, 288, 86, 288, 288, 388 and 882move to a circuit opening position and contact members 384, 388, 388,3I8, 3I2 and 3I4 of the switchin device 34 move to a circuit closingposition whereby the rectifiers I22, I24 and I26 are supplied from aseparate source of electrical energy. The circuits supplying therectifier-s I22, I24 and 428 under such conditions may be traced fromthe positive terminals of the separate sources of supply indicatedadjacent the individual controllers through contact members 386, 3I8 and3I4, respectively, of the switching device I34, rectifiers I22, I24 andI28, respectively, contact members 384, 388 and 3I2, respectively, ofthe switch ing, device I34 to the negative terminals of the separatesource of supply. With the rectifiers supplied in this manner, thecontrol field windings 98', I86 and H4 of the exciter generators 92, 84and 86, respectively, are so energized that the output of the excitergenerators effects the excitation of the main generators 74, I8 and I8,respectively, to cause an operation of the motors 58, 52 and 54,respectively, to raise the electrodes I6, I8 and 28, respectively.

As shown in Fig. 2 of the drawings, unless some other condition changesthe operation of the motors 58, 52 and 54 the limit switches areoperated before the movement of the electrodes'causes damage to thefurnace and system. For example the lug 368 carried by the electrode 28engages the trip switch 356 to interrupt the circuit to the fieldwinding II4 to prevent operation of the motor 54 so as to prevent theraising of the electrode 28 beyond a predetermined limit. Although notshown, similar limit switches are provided to control the positioning ofthe electrodes I6 and I8.

It is to be noted that as the contact members 324, 322 and 328 of thecircuit breaker 36 and contact members 288, 288 and 288, respectively,of the switching device I34 are in open circuit position they preventenergization of the field windings I88, I88 and H6, respectively, when ashort circuit condition for the electrodes I6, I8 and 28, respectively,is encountered.

As soon as the short circuit condition clears, even though the circuitbreaker is in its-circuit opening position where the contact member 328connects the ungrounded end of the winding 284 of relay 258 to conductor24, the winding 264 is again energized to cause the contact member 210to establish the energizing circuit for the winding 212 of theelectromagnet switching device I34. Under such conditions, the'contactmembers 324, 322 and 320 of the circuit breaker- 36 being in an opencircuit position prevents the energization of the field windings I00, IB'and II6 byany-fiow of current from the transformer the individualelectrodes I6, I8 and 20, the same may be accomplished by'o'perating theassociated individual controller I38, I and I42, respectively. Forexample, if it is desired to raise electrode 20, while maintainingautomatic operation or control of thepositioning of the electrodes I6 orI8, the handle 2 I2 of individual controller I42 is moved from, theautomatic position to the off position where the finger 2 I 4 passesthrough the notch 224 in the arcuate stop member 2I8 and the drum I94slides under the influence of the spring 220 to a position where thesegments carried by the drum I94 are in alignment with the cooperatingcontact fingers, The handle 2I2 is then turned to the raise positionwhere the segments 200, 202 and 204 engage cooperating contact fingers.In this position the segment 200 establishes a circuit from the currenttransformer 354 through the segment 200 directly to ground, therebypreventing an open circuit from the normal supply for the rectifier I26.time the segments 202 and 204 cooperateto establish a circuit extendingfrom the positive terminal of the separate source of supply throughsegment 204 of controller I42, contact member 302 of the switchingdevice I34, rectifier I26, contact member 300 of the switching deviceI34, segment 202 of the controller I42 to the negative terminal of theseparate'source of supply.

If instead of raising the electrode it is desired to lower the electrode20, the handle 2I2 is turned to the lower position where the segmentsI96 and I98 engage cooperating pairs of contact fingers to establish acircuit extending from the positive terminal of the separate source ofsupply At the same i through the segment I98, rectifier I32, contact 1tor 64 is a. reversible motor having an armature winding and aseparately excited'fleld winding 66, In order to control thedirection ofoperation' of the motor 54, a pair of contactors 362 and 364jareemployed for. so changing the fiow'of current'in themotor armature. asto'cause it to operate in the raise and lower directions respectively;The contactors 362 and 364 are provided with contact members 366 and368, respectively, disposed'for movement to predetermined circuit makingpositions depending upon the energizationof the {contactor windings 310and 312, respectively. a

As illustrated, one end of the contactor winding 310 is disposed to beconnected through a limit switch 356 to a terminal represented by thenegative symbol ofa separate source of supply and one end of'thecontactor winding 364 is disposed tobeconnected through a limit switch358 to the same terminal, the other ends of windings 31.0 and 312 beingdisposed to be selectively connected through contact member 314 of abalanced beam regulator 316 to the other terminal, representedbythe'positive symbol, of the separate source of supply when thecontrollers I 36 and I 42 are in the position shown. j The regulator316'is of a type well known having two energizing windings 318 and 380connected to be responsive to the are potential and the current flowingthrough the electrode 20, respectively, so that when the windings areenergized and the magnetic pulls are balanced the contact member 314isinan intermediate position as shown. Each of the motors and regulatorstherefore represented by the blocks 382 and 384' for electrodes I6 andl8,'respectively, are the same as the apparatus enclosedin the block 386for the electrodes 20 and therefore need not be further described.

' The controllers I38, I40 and I42 are similar having segments 388,390iand 392 in the lower, off and raise positions, respectively, whereasthe master controller I36 has three sets of corresponding segmentscomposed of segments 394, 396 and398 in the lower,, "01? and raisepositio'ns,'respectively, each set being associated with the regulatingapparatus for one of the electrodes. In ,this embodiment; theelectromagnetic switching device I34 is similar to that in theembodimentshown and described with respect to ,Figs. ,1A. and 1B in thatit has contact member 214 disposed for setting up the energizing circuitfor the relay 262 and consequently for the circuit eration of the motorI54 to effect the lowering of the electrode 20. The operation of thecontroller I42 can be duplicated for either controller I38 or I40 whereit is desired to effect independent positioning of the electrodes I6 andI8, respecvice I34, master controller I36 and individual con trollersI38, I40 and I42 being modified somewhat in accordance with the changesin the regulator and circuits required therefor.

g In the embodiment of Fig. 3. the electrode'rnog breaker 36. However,in this embodiment, the

electromagnetic switching. device has three sets of pairs of contactmembers 400 and 402 for cooperating in establishing predeterminedcircuits in conjunction with the master controller I36 and theindependent controllers I38, I 40 and I42.

Since'theregulators employed for controlling the operation of theelectrode motors in this embodiment are different from those illustratedin Figs.

1A and 1B, the circuit breaker 36 utilized in this embodiment isdevoidof the contact members 320,

322 and 324 utilized in the previous embodiment.

The operation of the embodiment of the inven- 'tion illustrated in Fig.3is somewhat similar to that ofthe. embodiment of the invention shownlin..Fig s., 1A and 1B in that the closing of the switch 266 establishesthe energizing circuit for the relay 258, the contact member 210 ofwhich establishes the energizing circuit for the winding 212 of theelectromagnetic switching device I34. When thus energized, contactmembers 214 and 400 of the switching device I34 are actuated to circuitclosingpositions and the contact memhers 462 of the switching device I34are actuated to circuit opening positions. The movement of the contactmember 214 .sets up the circuit which may be closed by manual operationof the switch 216 and extends through the contact member 216 of relay266 and the energizing winding 286 of relay 262 whereby the contactmember 282 closes the energizing circuit for the winding 284 of thecircuit breaker 36. When thus energized, the circuit breaker 36 moves toa circuit closing position where its contact members 36, 32, 34 and 318are in the circuit closing position and the contact member 328 is in acircuit opening position. As in the previous embodiment, when thecircuit breaker 36 is thus actuated to close the circuit for supplyingpower to the power transformer 28, the latch 336 of the latching device336 engages the lug 334 to maintain the circuit breaker in its circuitclosing position until the winding 328 of the latching device'isenergized in a predetermined manner.

With power supplied to the power transformer 23 in the manner described,the electrodes l6, I8 and 26 may be lowered to engage the charge I4 inthe furnace I6 and to establish an are by a movement or the mastercontroller I36 to the lower position where segment 394 engagescooperating contact fingersand a circuit for each of the regulators,described hereinafter with respect to only regulator 316, is closedextending from the positive terminal of a separate source of supplythrough contact member 1460 of the switching device I34, segment 394 ofthe. master controller I36, winding 312 of the contactor 364, limitswitch 358 to the negative terminal of the constant source of supply. Byestablishing this circuit the winding 312 is so energized that thecontact member 368 of the contactor 364 is actuated upwardly to acircuit closing position. The circuit thus established extends'from thepositive terminal of a separate source of supply through the contactmember 368, armature member 66 of the motor 54 and contact member'366 ofthe contactor 362 to the negative terminal of the separate source ofsupply, whereby the motor 54 is operated to eifect a lowering of theelectrode 26. Simultaneous positioning of the electrodes I6 and I8 isobtained by the operation of the motors and regulators in the blocks 382and 384 through the circuits established bythe associated seg-- ments394 of the mastercontrollerI36. As soon as the arc is established, themaster controller 436 is returned to its neutral position, wherebyautomatic operation of the electrode motor associated with eachelectrode is obtained in response to variations in the arc potential andare current.

For example, if the arc current should increase, the current flowingthrough the current transformer 356 so energizes the winding 386 of theregulator 316 as to overcome the balance or pull of the winding 318 andcause the contact memher 314 to move to a circuit closing position. Themovement of contact member 314 establishes a circuit extending from thepositive terminal of a separate source of electrical energy through thesegment 396 of master controller I36, segment 396 of controller I42,contact member 314, winding 316 Of contactor 362, and limit switch 356to the negative terminal of the separate source of supply whereby thewinding 316 is so energized as to effect a movement of the contactmember 365 upwardly to a circuit closing position. By establishing-thecircuit which exends from the positive terminal of the separate sourceof supply through the contact member 386, armature member 68 of themotor '54 and contact member 368 to the negative terminal of the sourceof supply, the motor 54 is operated to raise the electrode 26.

If the flow of current in the conductor'26 is large as, for example,where a short circuit is encountered, the current transformer 346 is soenergized as to efiect an operation of the protective device 346 toactuate its contact member '348 to a circuit closing positiontoeffectthe energization of the winding 328 of the trip device 336. Whenthis occurs the circuit breaker 36 is tripped and the contact member 326or the breaker establishes a circuit from the ungrounded end of winding264 of relay 258 to the conductor 24. If the short circuit still exists,the winding '264 is shunted to effect the deenergization thereof,whereby its contact member 216 .moves to an open circuit position todeenergize the winding 212 of the switching device I34 and cause thecontact members 214 and 466 to move to an open circuit position and thecontact members 462 to move to a. circuit closing position. The movementof the contact members 462 establishes circuits to effect the operationof the electrode motors to cause them to raise the electrodes. Thecircuits are similar for each of the regulators and may be understood byreference to the circuit extending from the positive terminal of aseparate source of supply, through contact member 462 Of the switchingdevice I34, winding 316 of contactor 362, limit switch 356 to thenegative terminal of the separate source of supply. The

, establishment of these circuits effects the operation of the electrodemotors to raise the respective electrodes.

As long as the short circuit condition on any one of the electrodes ismaintained, the contact member 326 of breaker 36 functions to effect theshunting of the winding .264 of relay 258. However, as soon as the shortcircuit condition is cleared, the winding 264 of relay 258 again becomesenergized whereby the operation of relay 258 effects theenergization of the switching device I34 to again establish the circuitsreferred to hereinbefore.

With the switching 'device'l34 and'the breaker 36 in their circuitclosing positions, if it is desired to independently effect thepositioning of any one of the electrodes I6, I8 and 26, theindi-vidualcontrollers I38, I46 and I42, respectively,,ca-n be movedtothe raise orlower position depending upon the changein position of the electrodesdesired. If, for example, it is desired tolower the electrode .26independently of the electrodes I6 and I8, only the controller I42is'moved to the lower position where thesegment 388 closes a circuitextending from the positive terminal of the source of supply throughcontact member 466 of switching device I34, segment 368 of controllerI42, winding-312 of contactor 364 and the .limit switch 358 to thenegative terminal of the separate source of supply. The closing of thiscircuit effects the energization of the contactor 364 whereby itscontact member 368 moves upwardly to establish the circuit to cause themo- ,tor 54 to operate in the direction to effect the lowering of theelectrode 26.

,If itis desired to raise the electrode. 28 ind pendently of theelectrodes I6 and 18, then the controller I42 is moved to the raise"position to establish the circuit extending-from thepositive terminal oftheseparate source-of supply through the segment, 392, winding 316 ofcontactor 362 and the limit switch 356 to the negative terminal of theseparate source of supply. The contactor 362 is thus energized toactuate its contact member 366 upwardly to establish a circuit to causea flow of current through the armature 60 in such a direction as toefiect the operation of the motor 54 in a direction to raise theelectrode 20.

The limit switches 356 and 358 are efiective for opening the circuits tothe winding 310 and 312, respectively, of the contactors 362- and 364,respectively, to prevent operation of the motor 54 to-move the electrodein-either the raise or lower direction beyond predetermined limits.Similar operation of the electrode motors may be had for controlling theposition of the electrodes l6 and Hi.

'In both of the embodiments described hereinbefore, it is, of course,apparent that the circuit breakers 36 may be moved to a circuit openingpositionat the will of the operator as the movement of the contactmember3l8 carried by the circuit breaker 36 to the circuit closingposition effects the energizationof the winding of relay 260 whereby thecontact member 218 is moved to a'circuit opening position to effect thedeenergization of the relay 262' and consequently the deenergization ofthewinding 284 of the circuit breaker. The operation of the relay 260 issubstantially instantaneous with the closing of the contact member 3! sothat the energizing winding 284 is deenergized even though the switch216 is held in a circuit closing position. Under such conditions, themanual operation of the switch 332 to a circuit closing position closesthe circuit from the separate source of supply through the winding 328of the trip device 336 to release the circuit breaker 36 at any timethat the operator desires to interrupt the circuit which supplies thepower to the power transformer 38.

By employing the circuits and apparatus of this invention, it isimpossible to reclose the circuit breaker against a short circuit fault,adequate provision having been made for effecting the clearing of thefault before a circuit breaker can be closed. The circuits and apparatusof this invention consequently prevent fiashover in the breaker,together with possible damage to the power transformer and regulatingequipment.

Theinvention utilizes standard apparatus and.

can be readily duplicated in the numerous types of regulating systemsnow available.

We claim as our invention: 1. In a system for controlling the feeding ofan electrode and the production of an electric,

are supplied from a source of power supply, in combination, a powertransformer connected to the electrode, a circuit breaker disposed toconnect the power transformer to the source of power, a winding for thecircuit breaker disposed;

I circuit breaker moves to a circuit opening position, a motor disposedfor raising and lowering the electrode, means responsive to the arcpotential to erect -"the operation of the motor to "lower the electrode,means responsive to the arccurrent to effect theoperation of the motorto raise the electrode, relay means disposed to be energized underpredetermined conditions to "connect the winding of the circuit breakerto be energized, another'relay means disposed to be energized when thecircuit breaker is in a circuit closing position to effect thedeenergization of the winding of the circuit breaker, means operableunder short circuit conditions of the electrode when the circuit breakeris in the circuit opening position to effect the deenergization of therelay means, and means responsive to the deenergization of the relaymean to connect the means responsive to the arc current to be energizedto eflfect the raising of the electrode.

2. In a'system for controlling the feeding of an electrode and theproduction of an electric arc supplied from a source of power supply, incombination, a power transformer connected to the electrode, a circuitbreaker disposed to connect the power transformer to the source ofpower, a winding for the circuit breaker disposed to be energized toactuate the circuit breaker to a circuit closing position, means fornormally holding the circuit breaker in circuit closing position, meansoperable under short circuit conditions of the electrode to release theholding means whereby the circuit breaker moves to a circuit openingposition, a motor disposed for raising and lowering the electrode, meansresponsive to the are potential to effect the operation or the motor tolower the electrode, means responsive to the arc current to effect theoperation of the motor to raise the electrode, relay means disposed tobe-energized under predetermined conditions to connect the winding ofthe circuit breaker to be energized, another relay means disposed to beenergized when the circuit breaker is in a circuit closing position toeffect the deenergization of the winding of the circuit breaker, meanscarried by the circuit breaker operable under short circuit conditionsof the electrode to effect the deenergization of the relay means whenthe circuit breaker is in the circuit opening position, and meansresponsive to the deenergization of the relay means to connect the meansresponsive to the arc current to be energized to effect the raising ofthe electrode. i

3.In a system for controlling the feeding of an electrode and theproduction of an electric arc supplied from a source of power supply, incombination, a power transformer connected to the electrode, a circuitbreaker disposed to connect the power transformer to the source ofpower, a winding for the circuit breaker disposed to be energized toactuate the circuit breaker to a circuit closing position, means fornormally holding the circuit breaker in circuit closing position, meansoperable under predetermined conditions to release the holding meanswhereby the circuit breaker moves to a circuit opening position, a motordisposed for raising and lowering the electrode, means responsive to theare potential to effect theoperation of the motor to lower theelectrode, means responsive to the arc current to effect the operationof the motor to raise the electrode, relay means disposed to beenergized under predetermined conditions to connect the winding of thecircuit breaker to be energized, another relay means disposed to beenergized when the circuit breaker is in a circuit closing positiontoeffect the deenergization of the winding of the circuit breaker, meansoperable under short circuit conditions of the electrode whenzthecircuit breaker is in the circuit opening position to effect thedeenergization of the relay means, and means carried by the relay meansdisposedwhen the relay means is deenergirtedv tov connect the meansresponsive to the are current to :be independently energized to effectthe raising of the electrode.

4. In a system forcontrolling the feeding of an electrode andtheproduction of an electric are supplied from a source of power supply,in combination, a power transformer connected to the electrode, acircuit breaker disposed to connect the power transformer to the sourceof power, a winding for the circuit breaker disposed to be energized toactuate the circuit breaker to a circuit closing position, means fornormally holding the circuit breaker in circuit closing position, meansoperable under short circuit conditions of the electrode to release theholding means whereby the circuit breaker moves to a circuit openingposition, a motor disposed for raising and lowering the electrode, meansresponsive to the are potential to effect the operation of the motor tolower the electrode, means responsive to the arc current to effect theoperation of the motor to raise the electrode,relay means disposed to beenergized under predetermined conditions to connect the winding of thecircuit breaker to be energized, another relay means disposed to beenergized when the circuit breaker is in a circuit closing position toeffect the deenergization of the winding of the circuit breaker, meanscarried by the circuit breaker operable under short circuitconditions-of the electrode to effect the deenergization of-therelaymeans when the circuit breaker is in the circuit opening position,and means carried by the relay means disposed when the relay means isdeenergized to connect the means responsive to the are current to beindependently energized to effect the raising of the electrode.

5. In a system for controlling the feeding of an electrode and theproduction of an electric are supplied from a source of power supply, incombination, a power transformer connected to the electrode, a circuitbreaker disposed to connect the power transformer to the source ofpower, a winding for the circuit breakerdisposed to be energized toactuate the circuit breaker to a circuit closing position, means fornormally holding the circuit breaker in a circuit closing position,means operable under short circuit conditions of the electrode torelease the holding means whereby the circuit breaker moves to a circuitOp position, means manually operable for also releasing the holdingmeans, a motor disposed for raising and lowering the electrode, meansresponsive to the arc potential to'efiect the operation of the motor tolower the electrode, means responsive to the arc current to effect theoperation of the motor to raise the electrode, relay means disposed tobe energized under predetermined conditions to connect the winding ofthe circuit breaker to be energized, another relay means disposed to beenergized when the circuit breaker is in a circuit closing position toeffect the deenergization of the winding of the circuit breaker, meansactuated by movement of the circuit breaker to the circuit openingposition to be operable under short circuit conditions only of theelectrode to effect the deenergization of the relay means, and meansresponsive to the deenergization of the relay means toconnect the meansresponsive to the arc current to beenergized to effect the raising ofthe electrode.

6. In a system for controlling the feeding of an electrode and theproduction of an electric are supplied from a source of power supply, incombination, a power transformer connected .to the electrode, a circuitbreaker disposed coconnect the power transformer to the source of power,a winding for the circuit breaker disposed to be energized to actuatethe circuit breaker to a circuit closing position, means for normallyholding the circuit breaker in circuit closing position, means operableunder short circuit conditions of the electrode to release the holdingmeans whereby the circuit breaker moves to a circuit opening position,means manually operable for also releasing the holding means, a motordisposed for raising and lowering the electrode, means responsiveto theare potential to effect the operation of the motor to lower theelectrode, means responsivetothe arc current to effect the operation ofthe motor to raise the electrode, relay means disposed to be energizedunder predetermined conditions to connect the winding of the circuitbreaker to be energized, another relay means disposed to be'energizedwhen the circuit breaker is in a circuit closing position to effect thedeenergization of the winding of the circuit breaker, means-actuated bymovement of the circuit breaker to the circuit opening position to beoperable under short circuit conditions only of the electrode to effectthe deenergization of the relay means, and means carried by the relaymeans disposed when the relay means is deenergized to connect the meansresponsive to the arc current to be independently energized to effectthe raising of the electrode.

7. In a system for controlling the feeding of an electrode and theproduction of an electric are supplied froma source of power supply, in

combination, a power transformer connected to the electrode, a'circuitbreaker disposed to connect the power transformer to the source ofpower, a winding for the circuit breaker disposed to .be energized toactuate the circuit breaker to a circuit closing position, means fornormally holding the circuitbreaker in circuit closing position, meansoperable under predetermined conditions to release the holding meanswhereby the circuit breaker moves to a circuit opening position, a motordisposed for raising and lowering the electrode, means responsivetothearc potential to effect the operation of the motor to lower theelectrode, means responsive to the are current to effect the operationof the-motor to raise the electrode, relay-means disposed to beenergized under predetermined conditions toconnect the winding of thecircuit breaker tobe energized, another relay means disposed to beenergized when the circuit breaker is in a circuit closing position toeffect the deenergization of the winding of the circuit breaker, theholding means maintaining the circuit breaker in circuit closingposition until the releasing mean is operated, means operable undershort circuit conditions only of the electrode when the circuit breakeris in a circuit opening position to effect the deenergization of'therelay means, and means carried by the relay means disposed when therelay means is deenergized to connect the means responsive to the arccurrent to be independently energized to effect the raising of theelectrode.

8. In a system for controlling the feedingof an electrode and theproduction of an electric are supplied from a source of power supply, incombination, a power transformer connected to the electrode, a'circuitbreaker disposed to connect the power transformer to the source ofpower, a winding for the circuit breaker disposed to be energized toactuate the circuit breaker to a circuit closing position, means fornormally holding the circuit breaker in circuit closing position,

a circuit closing position,

means operable under predetermined conditions to release the holdingmeans whereby the circuit breaker moves to a circuit opening position, amotor disposed for raising and lowering the electrode, means connectedto be responsive to the are potential to effect the operation of themotor to lower the electrode, means connected to be responsive to thearc current to efiect the operation of the motor to raise the electrode,relay means disposed to be energized under predetermined conditions toconnect the winding of the circuit breaker to be energized, anotherrelay means disposed to be energized when the circuit breaker is in acircuit closing position to effect the deenergization of the winding ofthe circuit breaker, means operable under short circuit conditions onlyof the electrode when the circuit breaker is in the circuit openingposition to effect the deenergization of the relay means, means operablewhen the circuit breaker is in the circuit opening position todisconnect the means responsive to the arc potential whereby the motorwill not operate to lower the electrode, and means responsive to thedeenergization of the relay means to connect the means responsive to thearc current to be energized to effect the raising of the electrode.

9. In a system for controlling the feeding of an electrode and theproduction of an electric are supplied from a source of power supply, incombination, a power transformer connected to the electrode, a circuitbreaker disposed to connect the power transformer to the source ofpower, a winding for the circuit breaker disposed to be energized toactuate the circuit breaker to a circuit closing position, means fornormally holding the circuit breaker in circuit closing position, meansoperable under predetermined conditions to release the holding meanswhereby the circuit breaker moves to a circuit opening position, a motordisposed for raising and lowering the electrode, means connected to beresponsive to the are potential to effect the operation of the motor tolower the electrode, means connected to be responsive to the arc currentto effect the operation of the motor to raise the electrode, relay meansdisposed to be energized under predetermined conditions to connect thewinding of the circuit breaker to be energized, another relay meansdisposed to be energized when the circuit breaker is in a circuitclosing position to efiect the deenergization of the winding of thecircuit breaker, means carried by the circuit breaker operable undershort circuit conditions only of the electrode to effect thedeenergization of the relay means when the circuit breaker is in thecircuit opening position, means operable when the circuit breaker is inthe circuit opening position to disconnect the means responsive to theare potential whereby the motor will not operate to lower the electrode,and means responsive to the deenergization of the relay means to connectthe means responsive to the arc current to be energized to effect theraising of the electrode.

10. In a system for controlling the feeding of an electrode and theproduction of an electric are supplied from a source of power supply, incombination, a power transformer connected to the electrode, a circuitbreaker disposed to connect the power transformer to the source ofpower, a winding for the circuit breaker disposed to be energized toactuate the circuit breaker to means for normally holding the circuitbreaker in circuit closing position,

9 means operable under predetermined conditions to release the holdingmeans whereby the circuit breaker moves to a circuit opening position, amotor disposed for raising and lowering the electrode, means connectedto be responsive to the arc potential to effect the operation of themotor to lower the electrode, means connected to be responsive to thearc current to effect the operation of the motor to raise the electrode,relay means disposed to be energized under predetermined conditions toconnect the winding of the circuit breaker to be energized, anotherrelay means disposedlto be energized when the circuit breaker is in acircuit closing position to effect the deenergization of the winding ofthe circuit breaker, means operable under short circuit conditions onlyof the electrode when the circuit breaker is in the circuit openingposition to efiect the deenergization of the relay means, means operablewhen the circuit breaker is in the circuit opening position todisconnect the means responsive to the are potential whereby the motorwill not operate to lower the electrode, and means carried by the relaymeans disposed when the relay means is deenergized to connect the meansresponsive to the arc current to be independently energized to effectthe raising of the electrode.

11. In a system for controlling the feeding of an electrode and theproduction of an electric are supplied from a source of power supply, incombination, a, power transformer connected to the electrode, a circuitbreaker disposed to connect the power transformer to the source ofpower, a winding for the circuit breaker disposed to be energized toactuate the circuit breaker to a circuit closing position, means fornormally holding the circuit breaker in circuit closing position, meansoperable under predetermined conditions to release the holding meanswhereby the circuit breaker moves to a circuit opening position, a motordisposed for raising and lowering the electrode, means responsive to thearc potential to effect the operation of the motor to lower theelectrode, means responsive to the arc current to effect the operationof the motor to raise the electrode, relay means disposed to beenergized under predetermined conditions to connect the winding of thecircuit breaker to be energized, another relay means disposed to beenergized when the circuit breaker is in a circuit closing position toeffect the deenergization of the winding of the circuit breaker, meansoperable under short circuit conditions only of the electrode when thecircuit breaker is in the circuit opening position to effect thedeenergization of the relay means, means responsive to thedeenergization of the relay means to connect the means responsive to thearc current to be independently energized to effect the raising of theelectrode, and means disposed to be manually operated to selectivelyconnect the means responsive to the are potential and the meansresponsive to the arc current to be independently energized when therelay means is energized to selectively lower or raise the electrode.

12. In a system for controlling the feeding of an electrode and theproduction of an electric are supplied from a source of power supply, incombination, a power transformer connected to the electrode, a circuitbreaker disposed to connect the power transformer to the source ofpower, a winding for the circuit breaker disposed to be energized toactuate the circuit breaker to a circuit closing position, means fornormally holding the circuit breaker in circuit closing position,

means operable under predetermined conditions to release the holdingmeans whereby the circuit breaker moves to a circuit opening position, amotor disposed for raising and lowering the electrode, means connectedto be responsive to the are potential to efiect the operation of themotor to lower the electrode, means connected to be responsive to thearc current to effect the operation of the motor to raise the electrode,relay means disposed to be energized under predetermined conditions toconnect the winding of the circuit breaker to be energized, anotherrelay means disposed to be energized when the circuit breaker is in acircuit closing position to effect the deenergization of the winding ofthe circuit breaker, means operable under short circuit conditions onlyof the electrode when the circuit breaker is in the circuit openingposition to effect the deenergization of the relay means, means operablewhen the circuit breaker is in the circuit opening position todisconnect the means responsive to the are potential whereby the motorwill not operate in response to the are potential, means responsive tothe deenergization of the relay means to connect the means responsive tothe arc current to be independently energized to effect the raising ofthe electrode, and means disposed to be manually operated to selectivelyconnect the means responsive to the arc potential and the meansresponsive to the arc current to be independently energized when therelay means is energized to selectively lower or raise the electrode.

13. In a system for controlling the feeding of an electrode and theproduction of an electric are supplied from a source of power supply, incombination, a power transformer connected to the electrode, a circuitbreaker disposed to connect the power transformer to the source ofpower, a winding for the circuit breaker disposed to be energized toactuate the circuit breaker to acircuit closing position, means fornormally holding the circuit breaker in circuit closing position, meansoperable under predetermined conditions to release the holding meanswhereby the circuit breaker moves to a circuit opening position, a motordisposed for raising and lowering the electrode, means connected to beresponsive to the are potential to effect the operation of the motor tolower the electrode, means connected to be responsive to the arc currentto effect the operation of the motor to raise the electrode, relay meansdisposed to be energized under predetermined conditions to connect thewinding of the circuit breaker to be energized, another relay meansdisposed to be energized when the circuit breaker is in a circuitclosing position to effect the deenergization of the winding of thecircuit breaker, means actuated by movement of the circuit breaker tothe circuit opening position to be operable under short circuitconditions only of the electrode to effect the deenergization oi therelay means, means operable when the circuit breaker is in the circuitopening position to disconnect the means responsive to the arc potentialwhereby the motor will not operate in response to the arc potential,means carried by the relay means disposed when the relay means isdeenergized to connect the means responsive to the arc current to beindependently energized to effect the raising of the electrode, andmeans disposed to be manually operated to selectively connect the meansresponsive to the are potential and the means responsive to the arccurrent to be independently energized when the relay means is energizedto selectively lower or raise the electrode.

JAMES P. HOUCK. RALPH A. GEISELMAN.

